1. Field of the Invention
Embodiments of the invention described herein pertain to the field of offshore oil and gas infrastructures. More particularly, but not by way of limitation, one or more embodiments of the invention enable a system, method and apparatus for subsea installation and removal of buoyancy modules.
2. Description of the Related Art
Oil and gas are often transported through pipelines on or beneath the ocean floor. These subsea pipelines are connected to onshore or offshore facilities for storage, processing or distribution of the oil and gas. Often, subsea pipelines connect to vessels or offshore platforms on the surface of the water through the use of submerged conduits, such as flexible risers, cables, umbilicals or steel catenary risers. The submerged conduits may carry oil, gas or other fluids or vapors to or from a pipeline end manifold or riser base. Submerged conduits may also be used to transfer oil or gas between a vessel or platform and an export tanker. The submerged conduits are usually maintained in a pre-defined geometric configuration such as an S-shape, lazy, steep, or pliant wave. Such configurations allow a vessel a full range of surface movement while it is connected to the conduit without placing excessive stress on the subsea lines, decouple wave movement from the seabed, and allow the submerged conduit to rise and lower without the possibility of kinks.
Submerged conduits maintain their configurations through the use of distributed buoyancy modules. Traditionally, buoyancy modules are installed on a conduit prior to its submersion under the water. However, buoyancy modules are often damaged after they are installed and after the conduit is already submerged. For example, buoyancy modules may be torn away from the submerged conduit or damaged in a collision. Accordingly, it is often desirable to remove or add a buoyancy module to a conduit after the conduit is already in place under water. Because buoyancy modules float and are difficult to handle under the water, present methods require that the submerged conduit be removed from the water in order to install or perform other maintenance on buoyancy modules, which is expensive, time consuming and undesirable.
For at least the limitations described above, there is a need for systems, methods and apparatuses for subsea installation or removal of buoyancy modules onto or from submerged conduits.